You may want to mark your sump with max water levels to ensure you never add to much water. That way, you dont have to worry about your tank flooding. Someone posted this video for me when I first started my tank and it helped me out alot; skip to 3:10 to see. [ame=http://www.youtube.com/watch?v=VYDU2B6sPfo&feature=mfu_in_order&list=UL]Episode 51 , pt3, How To Set Up A Reef Tank, LA Fishguys - YouTube[/ame]